Railway signaling apparatus



Nov. 17, 1942. Q M BACKER 2,301,995

RAILWAY sGNALING APPARATUS Filed Aug. l, 1939 f @www Y I i 12a! R4 C? 19 Cogpo! R6 Cipeaz'. Fig. 2.

lV ENTOR H15 ArroRNEY Caf Bacher.

Patented Nov. 17, 1942 RAILWAY SIGNALING APPARATUS Carl M. Backer, Pittston, Pa., assigner to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 1, 1939, Serial No. 287,731A

l Claims.

My invention relates tofrailway signaling apparatus, and particularly to signaling apparatus-for signal systems using coded current.

Railway code signal systems using time spaced impulses of direct current have been proposed, the codes being either of the polarity code type or of the frequency code type. For example, in a polarity code system-one code may consist of uniformly recurrent impulses of current of positive polarity, a second code may consist of uniformly recurrent impulses of current of negative polaru ity and such impulses of current alternately of positive and negative polarity may be used for a third code. In a frequency code type, the impulses of current may be all of the same polarity but of different rates, such as a rate of 180, 120 or 75 impulses per minute. Of course, a combination of different polarities and rates may be used if desired. Also, in such code systems it has been proposed to make the individual impulses of current of short duration, that is, the duration during which current flows is short as compared withrthe duration between successive impulses when no current ilows. Current impulses of short duration are desirable because they can be made of relatively high peak voltage as an aid to reliable operation of the signal system without an excessive energy output from the current sourcewhich ordinarily is a battery. In such systems, a code following relay responsive to such impulses of current is normally biased to one position to which it is moved by its biasing element when no code current flows and is energized and operated to a second position while a code current impulse perisists. Thus, the code following relay is operated to its second position for only a brief period in response to each individual impulse of current and is operated to its iirst position for a relatively long period between the successive impulses of current. In other words, the code following relay is operated at unequal on and ofi periods, the on periods when current flows being relatively short and the 01T periods when no current flows being relatively long. The decoding apparatus of such systems is selectively governed by the code following relay according to the diferent codes and a more satisfactory operation of such decoding apparatus is effected when the code following relay is operated at substantially equal on and oir periods.

Accordingly, a feature of my inventionvis the provision of novel and improved means where- With a code following relay or device is operated with substantially. equalA on and oii periods which automatically obtains substantially equall on and oit periods of operation over a relatively wide range of different code frequencies or rates. Again, a feature of my invention is the provision of code responsive apparatus of the type here contemplated? which is economical in construction and operation. Other objects and advantages of my invention will appear as the specification progresses.

I shall describe two forms of apparatus embodying my invention, and shall then point out the novel features thereof` in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view of one form of apparat-us embodying my invention when used with the train carried apparatus of a cab signal system. Fig. 2 is a diagrammatic view of a modication of the apparatus of Fig. 1 which also embodies my invention.

In each of the two views like reference characters designate similar parts.

Referring to Fig. 1, the reference characters la and Ib designate the track rails of a railway and to which rails code impulses of current are applied according to different traifc conditions/'of the railway. lViy invention is not concerned with either the means or the manner of applying the' code impulses of current to the rails la and lb and such apparatus is not shown for the sake of simplicity. A form of such code transmitting apparatus that may be used is disclosed and claimed in an application for'United States Letters PatentY Serial No. 222,883 filed August 3, 1938, by W. P; Place for Signal systems and now Patent No. 2,197,414.

It is suiiicient for the present application to point out that the track rails la and Ib are supplied with impulses of direct current ofV diierent polarity patterns'to reflect different trafiic conditions or are supplied with impulses of direct current of diterent code rates or frequencies to reiiect different traffc'conditions. In as'faras the'instant case is concerned the signicant feature of such impulses of current is the fact that the individual impulses are of short duration as compared with the durationbetween successive impulses of the same code. Also'that the duration between successive impulses of current may be different for different codes. To'illustrate such-circumstances, it-may beLpointed'A out thatwhen a code rate of 180 impulses per minute or 3 impulses per second is used, each code cycle is of substantially .33 second duration with current flowing (impulse of current) for, say, .05 second and no current ilowing for the remaining portion of the cycle or about .28 second. Again, if a cede rate of '75 impulses per minute or 11/5 impulses per second is used, each code cycle is of .80 second duration with current flowing for, say, .05 second the same as before and no current iiowing for substantially .'75 second. Again, the impulses of current may be of either positive or negative polarity, the duration of the impulses and the rate of occurrence being the same for the diiferent polarities. It will be understood, of course, that I do not wish to limit my invention to the code rates and duration of impulses cited above, and that other rates and durations may be used.

The reference characters 4 and 5 designate two train carried coils or inductors mounted on a train in the usual manner in inductive relationship with rails Ia and Ib, respectively. rIhe two inductors 4 and 5 are connected together in such manner that the electromotive forces induced therein in response to a code impulse of current ilowing in the rails are additive, and the two coils are connected across the input terminals of a detector-amplifier DA by means of wires 5 and 1.

The detector-amplier DA may be of any one of several well-known types and it is shown conventionally only for the sake of simplicity since its specic structure forms no part of my invention. The detector-amplifier DA may be that shown in the aforementioned Place application Serial No. 222,883 where electron tubes of the controlled ionization type are used with the tubes normally non-conducting and rendered momentarily conductive in response to each of the individual impulses of current flowing in the track rails.

A train carried code following relay MRI of the direct current neutral type is provided with two windings, the iirst winding being a pick-up winding 8 and the second windingr being a holding winding 9. The pick-up winding 8 of relay MRI is included in the output or anode circuit of detector-ampliner DA by means of wires I0 and II. It follows that when no electromotive force is being applied from inductors 4 and 5 across the input terminals of the detector-amplier DA, no current flows in the output circuit thereof and pick-up winding 8 of relay MRI is deenergized so that the contact lingers I2 and I3 of that relay fall by gravity into engagement with back contacts I4 and I5, respectively. At least there is no attractive force applied to contact fingers I2 and I3 by magnetic ux created by winding 8. When an electromotive force is applied from inductors 4 and 5 to the input terminals of detector-amplier DA in response to an impulse of current owing in the track rails, an impulse of current momentarily iiows in winding 8 of relay MRI and that relay is energized to attract contact fingers I2 and I3 into engagement with respective front contacts I6 and I'I. Consequently, the pick-up winding 8 of relay MRI is momentarily energized in response to each code impulse of the rail current and relay MRI is picked up and released once for each code impulse of current, the on period of relay MRI during which Contact lingers I2 and I3 engage the respective front contacts i6 and Il being short as compared with the ofi period during which contact iingers I2 and I 3 engage the respective back contacts I4 and I5 because of the short duration or' the code impulses of rail current.

The code following relay MRI controls a decoding relay DR, the circuit for decoding relay DR including one terminal of a battery I8, front contact IS-I'l of relay MRI, winding of relay DR and the opposite terminal of battery I8. Decoding relay DR is slow releasing in character and when periodically energized it remains picked up from one energizing impulse to the next. Decoding relay DR controls at its front contact I9 a signal circuit as desired. It is clear that with decoding relay DR receiving an energizing impulse of current only during the on period of code following relay MRI, it may not be eliectively energized because of the short period the relay MRI is picked up. That is to say, it is desirable that front contacts I3-II of code following relay MRI be retained closed for an interval long enough for the energization of decoding relay DR to build up to an eiective value.

To increase the on period of code following relay MRI so that the on period is substantially equal to the "oiT period and a more satisfactory control of decoding relay DR is effected, I provide equalizing apparatus which retains the code iollowing relay MRI picked up for an interval after the impulse of current applied to the pickup winding 8 ceases. This equalizing apparatus comprises condensers CI and C2, a charging resistor RI, a discharging resistor R2, a by-pass resistor R3, holding winding 9 of relay MRI and circuit connections with battery I8.

The equalizing apparatus can best be explained by describing its operation. During the oli period of relay lVIRI and its :back contact I2-I4 closed, the condenser CI is charged from battery I8 by a circuit that can be traced from the positive terminal of battery I8 over resistor RI, back contact I2-I4 of relay MRI, wire 2l), condenser CI, wire 2| and to the negative terminal of battery I8. Also, condenser C2 is charged by a circuit which includes the positive terminal of battery I8, resistor RI, back contact I2-I4 of relay MRI, Wire 20, condenser C2, resistor R3, wire 22, holding winding 9 of relay MRI, wires 23 and 2| and to the negative terminal of battery I8. The quantity of charge created on condensers CI and C2 depends, Within limits, on the time back contact I2-I4 of relay MRI is closed. With the polarity of battery I8 as indicated by the plus and minus signs, the right-hand plate of condenser CI and the lower plate of condenser C2 as viewed in Fig. 1 are positive and the left-hand plate of condenser CI and the top plate of condenser C2 are negative.

When the pick-up winding 8 of relay MRI is energized in response to a code impulse of rail current and relay MRI is picked up opening back Contact I2-I4 and closing front contact I2-I5, the condensers CI and C2 are disconnected from battery I8 and are connected with the holding winding 9 of relay MRI for discharge therethrough, condenser C2 being also connected with a closed discharging circuit to be shortly described. The discharge current from condenser CI tends to ilow from its positive plate over wire 28, front contact I2-IG of relay MRI, resistor R2, wire 22, holding winding 9 and wire 23 to the negative plate of condenser CI. The discharge current from condenser C2 tends to flow from its positive plate over wire 20, iront contact I2-I6 of relay MLRI, resistor R2, resistor R3 and to the negative plate of condenser C2. The discharge current from condenser C2 creates a voltage drop across resistor R2 which is of the same polarity as the voltage drop across resistor R2 as created by the discharge current from condenser CI. Hence, the discharge from condenser C2 increases the total IR drop across resistor R2 and such increase in the IR drop has the same effect as an increase in its ohmic resistance as far as the discharge current of condenser Cl is concerned. rihis action delays the discharge of condenser Ci. Condenser C2 is shortly discharged so that the IR drop across resistor R2 lessons and condenser Ci then discharges more quickly. The connection of winding 9 is such that the discharge current flowing therein creates a magnetiofflux that aids the flux created by the current impulse iiowing in pick-up winding 8. Consequently, the flux created by winding Si tends to retain the relay MR! picked up. The parts are so proportioned and adjusted that relay MRI is retained picked up by means of ux created through holding winding t for a period after the current impulse ceases t now in the pick-up winding 8 and relay MR! is operated with substantially equal on and oi periods. It the code rate is that of 75 impulses per minute, the f time back contact iiii4 of relay MRi is closed is relatively long and the charges created on condensers Ci and C2 are correspondingly large so that relay MRi is retained picked up by the discharge current through holding winding il for a correspondingly long period and substantially equal on and oir periods of operation of relay MRE obtains. Again, if the code rate is that of 180 impulses per minute, the time baci; contact !-4 is closed is correspondingly short and the charges built up on condensers Ci and C2 are correspondingly small so that the discharge current retains relay MRi picked up after the current impulse flowing in pick-up winding 8 ceases is correspondingly short and substantiaily equal on and ofi periods of relay MRI obtains. Consequently, nearly equal on and oi operation periods of relay MR! are eiifected over a relatively wide range of different code frequencies.

In Fig. 2, the train carried inductors 4 and 5 are mounted in inductive relation with track rails ia and Ib, and are connected with the input terminals of detector-amplifier DA the same as in Fig. l. In Fig. 2, the code following relay means consists of a first code following relay LR whose operating winding 24 is interposed in the output circuit of detector-amplifier DA, and a second code following relay MR which is controlled by the first relay LR through equalizincr apparatus embodying my invention. The eoualizing apparatus of Fig. 2 comprises condensers C3 and C4; resistors R4, R5, Rb and Rl; and connections with battery I, The code following relay MR of Fig. 2 in turn controls at its front Contact 25 decoding relay DR whose front contact I8 is interposed in a signal control circuit the same as in Fig. 1.

When no electromotive force is supplied from inductors 4 and 5 to the input terminals of detoeter-amplifier DA of Fig. 2, no current ovvs in the output circuit thereof and relay LR is deenergized closing its back contact 26 21. With relay LR thus released, condenser C3 is charged from battery I8 over a simple circuit which includes positive terminal of battery IS, resistor R6, back contact '2E- 21 of relay LR, resistor R4, condenser C3 and negative terminal of battery i8. When an electromotive force is applied from inductors 4 and E across the input terminals of detector-amplifier DA in response to a code impulse of current flowing in the track rails, an impulse of current momentarily flows in the winding 24 of relay LR and that relay is picked up opening back contact 25-21 and closing front C3 discharges through condenser C4, resistor R1,

front contact 26--28 of relay LR and resistor R4; and also through winding 29 of relay MR, resistors R5 and R1, front contact 2?-23 and resistor R4. Since the current impulse operating `relay LR is short, that relay immediately releases to reconnect condenser C3 with battery IB. The charge built up on condenser Cit now `discharges through winding 29 of relay MR and resistor R5. Relay MR is thus picked up and retained energized for an interval after the impulse of current from the detector-amplier DA ceases to flow in winding 24 of relay LR and relay LR releases. Condenser C soon discharges and relay MR is then released ready for the next code impulse. The extent to which condenser C3 is charged depends, within limits, on the time baci; Contact Z-Z'i of relay LR is closed and hence the charge built up on condenser C4 in response to the discharge from condenser C3 is proportional, within limits, to the rate at which relay LR is operated, with the result that the time relay MR is retained energized in response to the discharge from condenser C4 due to the charging thereof by the discharge of condenser C3 is greater for the slower code rate than for the higher Code rate. In other words, the relay MR is retained picked up for a longer period at the lower code rate than at the higher code rate. IV- have found that with proper proportioning of the parts the relay MR is operated with substantially equal on and oii periods at both the and 180 code rates. Furthermore, I have found that two code following relays when used as shown in Fig. 2 give substantially equal on and oit periods and critical adjustment in resistances and capacitors are not necessary. Also, contact adjustments of the relays are not critical.

It is to be pointed out that resistors R6 and Rl are provided to prevent sparldng at the contacts of relay LR. Hence, it is clear that resistances R6 and Rl may be omitted if desired, 'Ihat is to say, the resistors R4, R6 and R1 of Fig. 2 may be combined into one resistance R4.

Although I have herein shown and described only two forms of apparatus embodying my invention, is it understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In combination, a relay having a iirst and a second winding and biased to a rst position and operable to a second position when current momentarily iiows in said rst winding, a rst and a second condenser, a source of direct current, a resistor, means including a Contact of the relay closed at said first position to connect said condensers with said source to charge the condensers in parallel, means including said resistor and a contact of the relay closed at said second position to connect said first condenser with said second winding for energizing said relay after current ceases to now in the first winding, and

said second condenser connected across said resistor over said last mentioned relay contact to prolong the discharge of the first condenser through said second Winding.

2. In combination, a relay having a first and a second Winding and biased to a first position and operable to a second position when current momentarily flows in said rst Winding, a first and a second condenser, a source of direct current, a first and a second resistor, means including said first resistor and a rst position contact of said relay to connect said source with said condensers to charge said condensers in parallel, means including said second resistor and a second position contact of said relay to connect said rst coridonser with said second Winding to energize the relay, and said second condenser connected across said second resistor over the last mentioned relay Contact to increase the voltage drop across that resistor by the discharge from said second condenser to prolong the energization of said relay by the discharge from said first condenser,

3. In combination, a relay having a first and a second winding and a circuit controlling contact biased to a rst position and operable to a second position when either or both of said vin/iings are energized, a rst and a second condenser, a source ol direct current, a i'st and a second resistor; a first circuit including said first resistor and said rst position of said contact to connect said source or direct current across said rst condenser to charge the first condenser, said second condenser in series with said second Winding connected across said rst condenser to charge said second condenser in parallel with said rst condenser by said rst circuit, a second circuit including said second resistor and said second position of said contact to connect said first condenser to said second Winding to energize the second Winding to retain the Contact at its seoond position due to the discharge of the first condenser once said contact has been operated to said second position due to energization of said first Winding, and said second condenser connected across said second resistor over said second position oi said contact to control the rate at Which said rst condenser is discharged through the second Winding,

4. In combination, a two winding relay biased to a first position and operable to a second position when either one or both of its windings are energized, means connected to one of said Windings to momentarily energize said one Winding to operate the relay, a rst and a second condenser, a first, a second and a third resistor, a source of direct current, a rst circuit including a biased position contact of said relay and said first resistor to connect said direct current source to said first condenser to charge the rst condenser, said second condenser in series with said third resistor and the other one of said windings connected in parallel with said rst condenser to charge the second condenser by said rst circuit, a second circuit including an operated position contact of the relay and said second resistor to connect said first condenser to said other Winding to energize said other Winding by the discharge of the rst condenser to retain the relay at its operated position, and said second condenser in series with said third resistor connected across said second resistor over said operated position contact of the relay to increase the voltage drop across the second resistor due to the discharge of the second condenser to prolong the energization of said other winding by the discharge of the rst condenser.

CARL M. BACKER. 

